Prefabricated unit for refurbishment or construction of platforms

ABSTRACT

A prefabricated platform unit ( 1 ), for construction or refurbishment of a railway station platform, has a stepped upper surface ( 4 ) with a recessed planar forward portion ( 4   a ) on which edge copers ( 23 ) are to be mounted. Refurbishment of an exiting platform may be performed by excavating a region ( 22 ) of the platform surface to the front edge, installing a prefabricated platform unit ( 1 ) in the excavated region, and installing edge copers ( 23 ). Construction of a new platform may include the steps of constructing foundations alongside the railway, constructing upstanding supporting members on the foundations, and mounting a superstructure including the prefabricated platform units on the supporting members.

[0001] This invention relates to the construction of platforms forrailway stations.

[0002] The increasing demand for rail travel is requiring trainoperating companies to create extra capacity by the use of longertrains, but many existing station platforms are too short to accommodatesuch trains. The construction of platform extensions is restricted bythe requirement to minimise disruption to normal use of the existingplatform, to accommodate the works within existing train servicepatterns, and to have possession of the track while much of theconstruction work is carried out.

[0003] Many existing platforms were constructed in the nineteenth orearly twentieth century and do not comply with modern standards, inparticular with regard to track clearance, i.e. the distance between theplatform edge and the adjacent rail, which determines the gap acrosswhich a passenger has to step. When an existing platform is refurbished,it has to be brought up to standard.

[0004] It would therefore be desirable to be able to minimise the timefor which track possession is required when constructing or refurbishinga railway station platform. In particular it would be desirable to beable to provide a structure which can be constructed quickly, withoutusing time-consuming processes during possession.

[0005] In one aspect the present invention provides a prefabricatedplatform unit for construction or refurbishment of a railway stationplatform, the unit having a stepped upper surface, front and rear edgesurfaces, and side edge surfaces, the upper surface comprising a forwardportion, on which edge copers are to be mounted, and a rearward portion,with a step rising between the forward and rearward portions, theforward portion being planar.

[0006] In another aspect the invention provides a method of refurbishinga railway station platform, including the steps of excavating a regionof the surface of the platform, the said region extending to the frontedge of the platform, installing a prefabricated platform unit in theexcavated region, and installing edge copers on the installed unit.

[0007] In another aspect the invention provides a railway stationplatform structure comprising: foundations alongside the railway;upstanding supporting members rising from the foundations; cross beamsmounted on the supporting members and having cantilevered portionsextending beyond the supporting members towards the railway;longitudinal beams on the cross beams, each longitudinal beam extendingbetween a pair of the cross beams, there being at least two longitudinalbeams between each pair of cross beams, at least one of theselongitudinal beams being on the cantilevered portions of the cross beamsand at least one of these longitudinal beams being remote from thecantilevered portions; and platform units on the longitudinal beams, theplatform units having side edge surfaces extending away from the railwayand having front edge surfaces extending along the railway beyond theends of the cantilevered portions of the cross beams.

[0008] In another aspect the invention provides a method of constructinga railway station platform structure, including the steps of:

[0009] (a) constructing foundations alongside the railway;

[0010] (b) constructing upstanding supporting members on thefoundations; and

[0011] (c) mounting on the supporting members a prefabricatedsuperstructure comprising cross beams mounted on the supporting membersso that the cross beams have cantilevered portions extending beyond thesupporting members towards the railway, longitudinal beams on the crossbeams, and platform units on the longitudinal beams, side edge surfacesof the units extending away from the railway and front edge surfaces ofthe units extending along the railway beyond the ends of thecantilevered portions of the cross beams.

[0012] In another aspect the invention provides a method of constructinga railway station platform structure, including the following steps:

[0013] (a) constructing foundations alongside the railway;

[0014] (b) constructing upstanding supporting members on thefoundations;

[0015] (c) mounting cross beams on the supporting members so that thecross beams have cantilevered portions extending beyond the supportingmembers towards the railway;

[0016] (d) mounting longitudinal beams on the cross beams; and

[0017] (e) mounting platform units on the longitudinal beams so thatside edge surfaces of the units extend away from the railway and frontedge surfaces of the units extend along the railway beyond the ends ofthe cantilevered portions of the cross beams.

[0018] The invention will be described further, by way of example only,with reference to the accompanying drawings, in which:

[0019]FIG. 1 is a plan view of a prefabricated platform unit or slabunit primarily for refurbishment of an existing platform;

[0020]FIG. 2 is a side elevation of the slab unit;

[0021]FIG. 3 is an enlarged fragmentary vertical section taken on lineIII-III in FIG. 1;

[0022]FIG. 4 is an enlarged fragmentary vertical section taken on lineIV-IV in FIG. 1;

[0023]FIG. 5 is an exploded isometric view of an existing platform and arefurbished part of the platform;

[0024]FIG. 6 is an isometric view of three slab units, showing apreferred embodiment for use in the construction of a new platformstructure;

[0025]FIG. 7 is a vertical section through a platform structureincorporating the slab units of FIG. 6, in a first embodiment;

[0026]FIG. 8 is an exploded isometric view of the first embodiment ofthe platform structure;

[0027]FIG. 9 is a vertical section through a second embodiment of theplatform structure; and

[0028]FIG. 10 is an exploded isometric view of the second embodiment ofthe platform structure.

[0029] A prefabricated slab unit 1, primarily for use in therefurbishment of an existing platform, is shown in FIGS. 1 to 4; it is apre-cast concrete unit incorporating a reinforcing mesh 2. The slab unit1 has a planar bottom surface 3 and a stepped upper surface 4. The slabunit has a nominal width of 2 metres (for example) and has a rectangularoutline when viewed from above (FIG. 1). In the particular exampleshown, the outline is square. In general, the length of the slab unitfrom its front edge to its rear edge is at least equal to its width.Exemplary dimensions, in millimetres, are indicated in FIGS. 1 to 4. Theslab unit has a front edge surface 6, a rear edge surface 7, and sideedge surfaces 8,9, all of which are vertical surfaces. The upper surface4 has a forward portion 4 a which is planar and parallel to the bottomsurface 3, a rearward portion 4 b which is planar and slopes downwardlyand rearwardly from its front edge to its rear edge, and a step 4 cwhich rises vertically between the forward and rearward portions 4 a,4b. The step 4 c extends across the width of the slab unit, parallel toits front edge surface 6. In the forward portion there are severalthrough-holes 11 (one hole may be sufficient) for supplying grout to theunderside of the slab unit. The bottom surface 3 has a series ofparallel grooves 12 for selectively receiving a neoprene rubber sealingstrip 13 near the front edge surface 6. The side edge surfaces 8,9 havegrooves 10 along the length of the rearward portion 4 b, for receiving aneoprene rubber sealing strip (not shown).

[0030] The refurbishment of an existing platform will now be describedwith reference to FIG. 5. The existing platform comprises a front wall14 of brickwork with back filling supporting paving 16 (which maycomprise pre-cast slabs, bricks, or a layer of concrete, asphalt, orcoated macadam), with coping stones 17 projecting beyond the front wall14.

[0031] As a preliminary step, the platform surfacing is cut to a depthof 200 mm along a line 18 parallel to and spaced 2 metres from the frontedge of the platform and along lines 19 which are spaced 2 metres apartand extending from the front edge of the platform to the line 18. Inthis way a series of existing platform squares are defined. Thefollowing process is then carried out.

[0032] (1) One existing platform square is excavated to a depth of 200mm, without damaging the adjacent cut edges.

[0033] (2) Levelling elements in the form of shims or pads 21 arelevelled on the excavated region 22 and fixed.

[0034] (3) A slab unit 1, carried by a crane, is installed on the pads21, the sealing strip 13 being seated on the top of the front wall 14.The groove 12 selected to receive the sealing strip 13 will depend onthe relationship between the position of the wall 14 and the requiredposition of copers to be laid to define the platform edge.

[0035] (4) Grout is fed to the underside of the slab unit 1, using theholes 11. A preferred procedure is to inject the grout through the twoholes which are remote from the front edge surface 6 until grout entersthe two holes which are near the front edge surface 6. The sealing strip13 prevents escape of grout from under the front edge surface of theslab unit, thereby preventing staining of the front wall 14.

[0036] (5) Lightweight edge copers 23 are installed on quick-settingepoxy adhesive mortar on the forward portion 4 a. In the present examplefive edge copers 23 are mounted side by side across the two metre widthof the slab unit. Depending on the size of the edge copers, more orfewer may be used, although there are preferably at least four.Accordingly, the copers 23 are small enough to be handled without unduestrain, preferably weighing at most 25 kg if they are made of pre-castconcrete and being substantially lighter if they are made of less densematerials, for example plastics material. The edge copers 23 overlap thefront edge of the slab unit 1 and are laid level so that their frontedges are at a given horizontal and vertical spacing from the adjacentrail 24.

[0037] (6) Tactile paving elements 26 (which can be felt by a person'sfoot) are installed on quick-setting epoxy adhesive mortar, between thecopers 23 and the step 4 c, in such a manner as to compensate for anydifference in level between the rear edges of the copers 23 and thefront edge of the rearward portion 4 b of the upper surface of the slabunit.

[0038] The above described steps (1)-(6) are repeated until at leastpart of the length of the existing platform has been refurbished.

[0039] The above described process has to take place during trackpossession. However, because of the use of the pre-formed slab units 1,the work can be carried out quickly, keeping track possession time to aminimum.

[0040]FIG. 6 shows platform units or slab units 1 which are longer fromfront to back than the slab units of FIGS. 1 to 5 and which can be usedin the construction of a new platform structure, which may be anextension to an existing platform structure. In this case, the rearwardportion 4 b of the upper surface 4 is of greater length, has a moregradual slope (1 in 50) from front to back, and has a raised plinth 27near the rear edge surface 7 of the slab unit 1. A drainage outlet 28 isprovided in the front surface of the plinth 27. The forward portion 4 aof the upper surface has the same dimensions as in FIGS. 1 to 5, butthere are no grout holes. There is also no groove 12 in the underside ofthe slab unit. One side edge surface 9 has a key formation 29 forfitting in a recess or groove 31 in the opposite side edge surface 8 ofan adjacent slab unit so as to prevent relative vertical movement of theadjacent slab units. The bottom surface of the slab unit 1 hasintegrally cast projections 32 for a purpose to be explained below. Oneslab unit 1 has a recess 33 in one edge, for receiving a lighting column(not shown).

[0041] A first embodiment of a platform structure incorporating the slabunits 1 shown in FIG. 6 will now be described with reference to FIGS. 7and 8, by describing the steps involved in its method of construction.

[0042] (1) Simple temporary mesh fencing 34 is set up at a spacing of 2metres from the centre line of the outermost track rail 24 to define aborder between the so-called red zone (in which it would be hazardousand, in some situations, not permitted to work when not in trackpossession) and the so-called green zone (in which it is safe to workunder certain conditions, whether or not in track possession).

[0043] (2) In the green zone the ground is prepared and excavated toprovide two trenches parallel to the track. Concrete is then poured intothe trenches to form strip foundations 36.

[0044] (3) In situ concrete support columns 37 are constructed on thestrip foundations 36 and incorporate vertically projecting corrosionresistant threaded tie bars of 16 mm diameter (not shown in FIG. 8).

[0045] (4) Pre-cast concrete cross beams 38 are craned in and positionedon the support columns 37. Each cross beam 38 is supported by twocolumns 37 and has a cantilevered portion 38 a extending beyond thesupport columns 37 towards the track. Each cross beam 38 has twovertical through holes 39, which are formed during the casting of theconcrete cross beam and which have a minimum diameter of 50 mm. Theseoversize holes 39 receive the threaded bars projecting upwards from thecolumns 37 and are used to locate the cross beams 38 relative to thesupport columns 37, nuts being threaded on the tie bars to provide amechanical connection between the cross beam 38 and the support columns37. Resilient rubber pads (not shown) with pre-formed holes to receivethe threaded bars are located on top of the columns 37. The cross beams38 incorporate holding down bolts (not shown) for connecting the base ofthe lighting column and one or more ducts 41 for the passage ofelectrical cables.

[0046] (5) Pre-cast longitudinal beams 42 are craned in and mounted onthe cross beams 38. The upper edges of the cross beams 38 have recesses43 which accommodate end portions 42 a of the beams 42 resting onresilient rubber pads 44 at the bottoms of the recesses 43. Abutmentsurfaces 42 b (recessed beneath the end portions 42 a) face therespective side surfaces of the cross beams 38. The upper surfaces ofthe cross beams 38 are flush with the upper surfaces of the longitudinalbeams 42.

[0047] (6) The slab units 1 are craned in and mounted on the supportingstructure constituted by the cross beams 38 and longitudinal beams 42.The downward projections 32 on the slab units abut against respectiveside surfaces of two of the longitudinal beams 42 to locate the slabunits in the direction towards and away from the track. The slab units 1are installed one by one, engaging the key formation 29 on each slabunit with the corresponding groove 31 of the next slab unit. The jointsbetween adjacent units are sealed by a dry rubber O-ring which, whencompressed, forms a watertight seal. To assist installation, temporarylifting rings (not shown) can be fitted to anchorages (not shown)located in or near the plinth 27 and in the forward portion 4 a of theupper surface of the slab unit.

[0048] (7) Platform fencing (not shown) is erected on the plinths 27 andelectrical cabling is installed using the cable ducts 41 and cablesupport trays 46 mounted in facing longitudinal recesses 47 in a pair ofthe longitudinal beams 42.

[0049] (8) Platform lighting is installed, a lighting column beinginserted through the recess 33 in at least one of the slab units 1 andbolted to the cross beam 38 below.

[0050] (9) Lightweight copers 23 and tactile paving elements 26 are theninstalled on the forward portions 4 a of the upper surfaces 4 of theslab units 1 (in the manner described above with reference to FIG. 5).

[0051] (10) Anti-debris netting (not shown) is installed beneath theplatform, by means of stainless steel eyes received in sockets (notshown) cast in the cross beams 38.

[0052] (11) Finally the temporary fencing 34 is removed.

[0053] It will be appreciated that steps (2), (3), (7), and (10) do notrequire track possession. The design of the platform structure ensuresthat the other steps, which will normally require track possession, canbe carried out quickly and in separate stages.

[0054] A second embodiment of the platform structure will now bedescribed with reference to FIGS. 9 and 10. The second embodimentdiffers from the first embodiment only in using piles instead of stripfoundations. Accordingly, the above description, except for step (2), isapplicable to the second embodiment and will not be repeated.

[0055] In the construction of the second embodiment, step (2) isreplaced by the step of preparing the ground and inserting piles 36 ainto the ground at the intended locations of the supporting columns 37,which are subsequently constructed on the piles.

[0056] Various modifications may be made within the scope of theinvention. In particular, the lengths of the cross beams 38 and thenumber of longitudinal beams 42 between each pair of cross beams may bevaried to suit different platform widths (front to back). For a platformwidth of less than 3 metres (for example 2.5 metres) two longitudinalbeams 42 may be sufficient. For platform widths of 3 or 3.5 metres,three longitudinal beams 42 may be sufficient. For a platform width of 4metres, four longitudinal beams should be used. The position of thefront longitudinal beam in relation to the front end of the cross beamwill be the same in each case, so that pre-cast concrete manufacture ofthe cross beams can to some extent be standardised.

[0057] To accommodate curved track alignments the side edges of one ormore of the slab units may be non-parallel, either converging ordiverging away from the front edge, one or both of the side edges notbeing perpendicular to the front edge.

[0058] Cable-tray receiving grooves 47 may be provided in more than twoof the longitudinal beams 42, and additional holes 41 may be provided inthe cross beams 38 if one or more additional cable trays are fittedusing these grooves.

[0059] To simplify construction of the superstructure on the supportcolumns 37, the platform units 1 may be combined with the longitudinalbeams 42 as prefabricated units, or longitudinal and cross beams may becombined as prefabricated units, or platform units and longitudinal andcross beams may be combined as prefabricated units. In each case thespacing of the supporting columns 37 would be reduced by approximatelyone half, the width of the prefabricated units being correspondinglyreduced in order to keep the weight to be lifted within practicablelimits.

[0060] Instead of fitting the edge copers and tactile paving elements onthe slab units after the installation of the slab units, it may bepossible to fit them on the slab units before the slab units are mountedon the supporting structure. It may also be possible to combine thetactile paving elements with the edge copers, or to omit the tactilepaving elements.

[0061] The platform structure can be provided at any trackside locationwhere it may be desired to bring a train to a halt in order to allowpassengers or train operating staff to board or alight from the train orto attend to the maintenance of the exterior of the train.

1. A prefabricated platform unit for construction or refurbishment of arailway station platform, the unit having a stepped upper surface, frontand rear edge surfaces, and side edge surfaces, the upper surfacecomprising a forward portion, on which edge copers are to be mounted,and a rearward portion, with a step rising between the forward andrearward portions, the forward portion being planar.
 2. A unit asclaimed in claim 1, in which the rearward portion of the upper surfaceslopes downwardly and rearwardly from adjacent the step.
 3. A unit asclaimed in claim 1 or 2, in which the rearward portion of the uppersurface has a raised plinth adjacent the rear edge surface.
 4. A unit asclaimed in any preceding claim, in which one of the side edge surfaceshas a key formation for fitting in a recess in a side edge surface of anadjacent unit.
 5. A unit as claimed in any preceding claim, in which oneof the side edge surfaces has a recess for receiving a key formation ona side edge surface of an adjacent unit.
 6. A unit as claimed in anypreceding claim, in which the unit is made of reinforced concrete.
 7. Aunit as claimed in any preceding claim, in which the length of the unitfrom front to rear is at least as great as its width.
 8. A unit asclaimed in any preceding claim, in which the unit is about 2 metreswide.
 9. A unit as claimed in any preceding claim, in which the lengthof the forward portion of the upper surface from the front edge surfaceto the step is at least 1 metre.
 10. A unit as claimed in any precedingclaim, the unit being in the form of a slab having a substantiallyplanar bottom surface, the forward portion of the upper surface beingsubstantially parallel to the bottom surface.
 11. A unit as claimed inclaim 10, in which the unit has at least one through-hole communicatingbetween the forward portion of the upper surface and the bottom surface,for supplying grout to the underside of the unit.
 12. A unit as claimedin claim 11, in which the bottom surface has a groove for receiving aseal adjacent the front edge surface.
 13. A unit as claimed in any ofclaims 10 to 12, in which the bottom surface has projections forlocating the unit relative to a supporting structure.
 14. A method ofrefurbishing a railway station platform, including the following steps:(a) excavating a region of the surface of the platform, the said regionextending to the front edge of the platform; (b) installing in theexcavated region a prefabricated platform unit according to any ofclaims 1 to 13; and (c) installing edge copers on the forward portion ofthe upper surface of the installed unit.
 15. A method as claimed inclaim 14, in which, between steps (a) and (b), levelling elements arearranged in the excavated region to support the unit.
 16. A method asclaimed in claim 14 or 15, in which, between steps (b) and (c), grout issupplied to the underside of the unit.
 17. A method as claimed in claim16, in which the grout is supplied through at least one hole in theforward portion of the upper surface of the unit.
 18. A method asclaimed in claim 17, in which escape of grout from under the front edgeof the unit is substantially prevented by a seal between the unit andthe excavated region.
 19. A method as claimed in any of claims 14 to 18,in which at least four edge copers are mounted side by side across thewidth of the unit.
 20. A method as claimed in any of claims 14 to 19, inwhich the width of each edge coper is less than its length.
 21. A methodas claimed in any of claims 14 to 20, in which each edge coper weighs atmost 25 kg.
 22. A method as claimed in any of claims 14 to 21, in whichthe edge copers are installed on a quick-setting resin-based mortar. 23.A method as claimed in any of claims 14 to 22, in which, after step (c),paving elements are installed between the edge copers and the step inthe upper surface of the unit.
 24. A method as claimed in any of claims13 to 22, in which, before step (a), the platform is cut to a givendepth along lines delimiting a rear edge and side edges of the region tobe excavated.
 25. A railway station platform structure comprising aplurality of platform units according to any of claims 1 to 13 arrangedside by side.
 26. A platform structure as claimed in claim 25, in whichthe units carry edge copers mounted side by side on the forward portionsof the upper surfaces of the units, the front edges of the copers beingat a given horizontal spacing from the adjacent rail.
 27. A platformstructure as claimed in claim 26, including paving elements between theedge copers and the steps in the upper surfaces of the units.
 28. Aplatform structure as claimed in claim 27, in which the paving elementshave tactile upper surfaces.
 29. A railway station platform structurecomprising: foundations alongside the railway; upstanding supportingmembers rising from the foundations; cross beams mounted on thesupporting members and having cantilevered portions extending beyond thesupporting members towards the railway; longitudinal beams on the crossbeams, each longitudinal beam extending between a pair of the crossbeams, there being at least two longitudinal beams between each pair ofcross beams, at least one of these longitudinal beams being on thecantilevered portions of the cross beams and at least one of theselongitudinal beams being remote from the cantilevered portions; andplatform units according to claim 1 on the longitudinal beams, the sideedge surfaces of the platform units extending away from the railway andthe front edge surfaces extending along the railway beyond the ends ofthe cantilevered portions of the cross beams.
 30. A platform structureas claimed in claim 29, in which the supporting members comprisecolumns.
 31. A platform structure as claimed in claim 29 or 30, in whicheach cross beam is supported by two said supporting members.
 32. Aplatform structure as claimed in any of claims 29 to 31, in which thesupporting members and the cross beams have complementary formationswhich interengage to locate the cross beams relative to the supportingmembers.
 33. A platform structure as claimed in claim 32, in which thesaid formations on the supporting members comprise tie bars and the saidformations on the cross beams comprise through-holes.
 34. A platformstructure as claimed in any of claims 29 to 33, in which the cross beamare connected to the supporting members solely by mechanical connectiondevices.
 35. A platform structure as claimed in any of claims 29 to 34,in which the cross beams have upwardly and laterally open recesses whichaccommodate end portions of the longitudinal beams.
 36. A platformstructure as claimed in claim 35, in which resilient pads are interposedbetween the said end portions and the bottoms of the said recesses. 37.A platform structure as claimed in claim 35 or 36, in which thelongitudinal beams have end abutment surfaces recessed beneath the saidend portions.
 38. A platform substructure as claimed in any of claims 29to 34, in which the cross beams are integral with the longitudinalbeams.
 39. A platform structure as claimed in any of claims 29 to 38, inwhich the upper surfaces of the cross beams are substantially flush withthe upper surfaces of the longitudinal beams.
 40. A platform structureas claimed in any of claims 29 to 39, in which at least one pair ofadjacent longitudinal beams, between an adjacent pair of cross beams,have longitudinal recesses which face each other, for receiving a cablesupport tray.
 41. A platform structure as claimed in any of claims 29 to40, in which at least one of the cross beams has at least one transverseaperture for the passage of a cable.
 42. A platform structure as claimedin any of claims 29 to 41, in which the undersides of the platform unitshave projections for locating the platform units relative to thelongitudinal beams.
 43. A platform structure as claimed in any of claims28 to 42, in which each longitudinal beam supports at least two platformunits.
 44. A platform structure as claimed in any of claims 29 to 41, inwhich the longitudinal beams are integral with the platform units.
 45. Aplatform structure as claimed in any of claims 29 to 44, in which theadjacent side edge surfaces of adjacent platform units have,respectively, a key formation and a recess in which the key formationfits so as to resist relative vertical motion of the adjacent slabunits.
 46. A platform structure as claimed in any of claims 29 to 45, inwhich each platform unit is elongate in the direction away from therailway.
 47. A platform structure as claimed in any of claims 29 to 46,in which the platform units include raised portions which are aligned toconstitute a plinth to the rear of the platform structure.
 48. Aplatform structure as claimed in any of claims 29 to 47, furthercomprising edge copers mounted side by side on the platform units.
 49. Amethod of constructing a railway station platform structure, includingthe steps of: (a) constructing foundations alongside the railway; (b)constructing upstanding supporting members on the foundations; and (c)mounting on the supporting members a prefabricated superstructurecomprising cross beams mounted on the supporting members so that thecross beams have cantilevered portions extending beyond the supportingmembers towards the railway, longitudinal beams on the cross beams, andplatform units according to claim 1 on the longitudinal beams, the sideedge surfaces of the platform units extending away from the railway andthe front edge surfaces of the platform units extending along therailway beyond the ends of the cantilevered portions of the cross beams.50. A method as claimed in claim 49, in which the longitudinal beams arecombined with the platform units and step (b) includes mounting thecross beams on the supporting members and then mounting the longitudinalbeams together with the platform units on the cross beams.
 51. A methodas claimed in claim 49, in which the cross beams, the longitudinalbeams, and the platform units are combined to form separateprefabricated units of the superstructure, and step (b) includesmounting the prefabricated units of the superstructure on the supportingmembers.
 52. A method of constructing a railway station platformstructure, including the following steps: (a) constructing foundationsalongside the railway; (b) constructing upstanding supporting members onthe foundations; (c) mounting cross beams on the supporting members sothat the cross beams have cantilevered portions extending beyond thesupporting members towards the railway; (d) mounting longitudinal beamson the cross beams; and (e) mounting platform units according to claim 1on the longitudinal beams so that the side edge surfaces of the platformunits extend away from the railway and the front edge surfaces of theplatform units extend along the railway beyond the ends of thecantilevered portions of the cross beams.